Why do immunosuppressive drugs harm health and shorten life?

Chris Smith answered the question...

The reason is that the immune system is there for a reason. And if you have to take drugs to deactivate the immune system, they don’t just deactivate the bit of the immune system that is potentially attacking the new organ or the graft, they suppress the entire immune system. This means that you’re at a greater risk of getting infections from various sources: bacterial sources, viral sources, fungal sources; so that can have an impact.

But, also your immune cells patrol your body looking for cancer and there is, therefore, a higher risk that some of your cells may become cancerous and not be removed by the immune system because it’s being deactivated.

There’s also a third thing which is that the drugs themselves are poisonous. Every drug that we take can has side effects, and so, if you take a drug into your body, there will be side effects and some of these drugs do themselves have damaging effects on end organs including your kidney, for instance, and the liver, sometimes. As a result of that, that can also render you slightly less healthy.

So all these things add together to a slight reduction in health. But, of course, that’s tiny in proportion to the enormous benefit returned to you by having had a transplant of, say, a heart, or a lung, or a liver or, in this case, we’re talking about a limb...